The invention relates to a magnetic card reader, and more particularly to a magnetic card reader including a novel backup means which urges a magnetic card against a transducer as it is moved through a guide channel.
When a magnetic head or transducer is utilized to read a code from a sound track in a stripe formed by a magnetic medium formed on a card, it is necessary that the magnetic core of the transducer be maintained in close contact with the stripe surface. In a known reader of the type in which a card is conveyed at a given rate by an electric motor, the card is fed past the transducer by a drive belt or feeder roller after it is introduced into the guide channel, there is provided a backup roller or capstan on the opposite side of the guide channel at a position opposite to the transducer for urging the card against the transducer. Such backup roller or capstan comprises a cylindrical body which is rotatable about a fixed axis, and is formed of a resilient material such as a rubber. In order to orient the card in a manner such that the stripe surface of the card be maintained in exact engagement with the yoke or magnetic core of the transducer, the cylindrical surface of the backup roller or capstan must maintain a linear contact with the opposite surface of the card with a uniform pressure. This requires that the backup roller or capstan be formed so as to have a uniform outer diameter throughout its length and that its axis be correctly aligned. However, it is difficult to maintain such requirements over a prolonged period of use. This difficulty is caused by the fact that cards, such as a bank card, credit card or passenger ticket, for example, which are owned by a multiplicity of users are not always maintained in a flat condition, but may be distorted, folded or creased. If such a distorted card is passed through the card reader, the surface of the backup roller or capstan may be subject to a localized abrasion or its axis may be urged to become eccentric. To compensate for such abrasion or eccentricity, the backup roller or capstan may be initially biased to engage the card with an increased pressure. However, this results in an increased friction between the magnetic coating of the card and the transducer, thereby damaging the card.
On the other hand, in a recently developed card reader in which a card is manually operated, the card may be passed through the guide channel in varying orientations depending on the manner of use, so that some provision is necessary to maintain a proper engagement between the magnetic stripe of the card and the surface of the transducer. To this end, there has been a proposal to provide a backup roller which is similar to the one used in the motor fed card reader. However, in a manually fed card reader, the backup roller is subject to an increased damage since a hard card having a vinyl chloride base, as prescribed by the Bankers Association of various countries, may be brought against the backup roller with an irregular operating pressure or impact, depending on the manner of use by the users. In addition, damage may be caused to the backup roller for other reasons.